1. Field of the Invention
The present invention relates to a disk reproducing apparatus and a disk reproducing method. In particular, the invention relates to a disk reproducing apparatus and a disk reproducing method for reproducing a binary input signal.
2. Description of Related Art
In recent years, there is an increasing demand to downsize an optical disk and record information on the optical disk with a higher density. To meet such a demand, an edge recording system has been proposed.
According to the edge recording system, in the case of recording data as a binary code string based on 1 and 0, light intensity data is inverted with a bit “1” to create a recording light beam emission pattern and irradiate an optical disk with a recoding light beam.
Such an edge recording system places importance on an edge position, and needs to read data with the edge position being fixed and reproduce the data.
However, an error occurs at the time of reading data due to various factors such as a laser irradiation power or inclination of a disk surface, and the data cannot be correctly reproduced in some cases.
To overcome such defects, a support for the read data such as an error correction function has been provided, but the most important thing is to minimize an error in reading data.
As a method of minimizing the error, there has been proposed a method of measuring a pulse width at the time of detecting an edge to shorten the pulse width in inverse proportion to the measurement result (for example, see Japanese Unexamined Patent Application Publication No. 5-81678). This method is devised to deal with a situation that a pulse width of a read signal is larger than an actual recorded data but has a problem in that an error cannot be corrected when a pulse width shorter than that of the recorded data is measured.
Further, a double-edge detection method capable of detecting both edges to more accurately read data has bee also proposed (for example, see Japanese Unexamined Patent Application Publication No. 7-169059). However, this method needs to detect both of a rising edge and a falling edge and thus disadvantageously requires a complicated circuit configuration.